Acoustic thermometry of ocean climate and the global ocean observing system.

Abstract

The uniqueness and sustainability of acoustic measurements of basin‐scale temperature were demonstrated by the the Acoustic Thermometry of Ocean Climate and North Pacific Acoustic Laboratory programs in the North Pacific over the decade 1996–2006. Tomography has a role to play in the global observing system as a measurement type that complements altimetry and profiling floats. Tomography is a subsurface measurement of temperature; salinity contributes negligibly. Acoustic travel times are inherently precise integral measurements of temperature; mesoscale variability is supressed. Tomographic measurements offer one of the few ways to sample the abyssal ocean. The North Atlantic and Arctic have been highlighted by international conferences as regions that would be suitable for implementing tomographic arrays. Ocean basins can be measured by tomography using a few acoustic sources and receivers, employing platforms of opportunity such as existing or planned components of the ocean observing system. Extensive acoustic sampling can be achieved by sharing resources, while minimizing long‐term operation and maintenance costs. Because of the integral nature of the data, tomography is best employed in conjunction with numerical ocean models and data assimilation. [Dushaw et al., “a global ocean acoustic observing network,” OceanObs’09: Sustained Ocean Observations and Information for Society, ESA Publication No. WPP‐306].